The present invention relates, in general, to dosimetry and therapeutic implants and, in particular, to an apparatus and method for determining the locations of brachytherapy seeds and other therapeutic seed implants.
Ionizing radiation is used medically in a wide range of therapeutic procedures and treatments. Brachytherapy techniques, involving the implantation of radioactive xe2x80x9cseedsxe2x80x9d in a defined array, often are used to deliver controlled doses of radiation to specific regions and parts of the body. Typically, a diseased organ or other to structure, such as a tumor, is the target of the applied radiation. For example, in the treatment of prostate cancer, a prescribed number of radioactive seeds that serve to deliver controlled doses of radiation to the prostate are implanted at desired locations in the prostate.
Generally, it is desirable, and in many instances it is mandatory, to restrict the exposure to radiation to pathological regions and to minimize the effect of radiation on surrounding healthy structures. Treatment planning techniques that specify a three-dimensional matrix of radioactive seed implant placements attempt to achieve this result.
Due to difficulties and limitations in the ability of the attending physician to position the therapeutic seeds at the desired locations, the actual matrix of therapeutic seeds might be different from the one that is intended. As a result, the surrounding tissue can be is exposed to undesired amounts of radiation, while portions of the targeted pathological tissues might be underexposed and not receive the desired degree of radiation.
It is common practice to view the therapeutic seed implantations with CT or MRI equipment after the implantations have been completed to confirm that the therapeutic seeds have been positioned properly. Such a viewing of the implanted therapeutic seeds is very expensive and time consuming. When improperly implanted seeds are detected, corrections are made by implanting additional seeds at the desired locations, thereby subjecting the patient to another implantation procedure. This, of course, is undesirable because the implantation procedure is uncomfortable for the patient and exposes the patient to the risks associated with any such medical procedure.
Ultrasonic imaging often is used in conjunction with radiotherapy to locate target tissue structures and guide the therapy procedure. With brachytherapy, real-time ultrasonic images are used to guide the placement of the radioactive therapeutic seeds. Once the matrix of implanted seeds is in place, however, it is difficult to determine the locations of the implanted seeds because of acoustic reflections, shadowing and trauma-induced increases in tissue echogenesis. Consequently, it is still necessary to confirm, with CT or MRI equipment after the implantations have been completed, that the implanted seeds have been positioned properly.
Apparatus for determining the locations of therapeutic seeds implanted in a body part, constructed in accordance with the present invention, includes means for causing each of the implanted seeds to undergo a physical change that can be sensed and sensing means for detecting the physical changes of the implanted seeds and developing signals representative of the physical changes of the implanted seeds. Such apparatus, constructed in accordance with the present invention, also includes indicating means responsive to the signals developed by the sensing means for developing indications of the locations of the implanted seeds.
A method for implanting therapeutic seeds in a body part, conducted in accordance with the present invention, includes the steps of establishing desired locations in a body part for the implantation of a plurality of therapeutic seeds and implanting the plurality of therapeutic seeds in the body part. Also included in this method are the steps of causing each of the therapeutic seeds to undergo a physical change and identifying the therapeutic seeds by sensing the physical changes in the therapeutic seeds. This method further includes the steps of determining the locations of the therapeutic seeds from the identifications of the therapeutic seeds, comparing the determined locations of the therapeutic seeds with the desired locations of the therapeutic seeds and correcting the locations of those therapeutic seeds that are not implanted at the desired locations.
It is to be understood that both the foregoing general description of the present invention and the following detailed description of the present invention are exemplary, but are not restrictive, of the present invention.